A burner of this type is disclosed in German Patent DE 2 905 746.
This known burner comprises, in addition to a central fuel admission for the oil, another fuel admission disposed concentrically thereto for powdered coal or any other like fuel.
For the purpose of obtaining a good mixture, this solid fuel admission lies between two streams of primary air, of which one, which is the central stream, is set in rotation or eddy, i.e. it comprises a component in tangential or peripheral direction, and of which the other, outer, stream comprises an essentially axial flow velocity for the purpose of stabilizing the flame which penetrates far in the rotary furnace.
In other known burners, the stream of primary air is also provided to extend relatively far in the interior.
The known burner comprises, at its centre, a liquid fuel, generally oil, admission. The liquid fuel is atomized into fine droplets by means of a spray nozzle and is mixed, after leaving the central opening of the nozzle, with primary air which issues from the opening for outlet of eddying air, which opening is located radially around the central opening.
The known burners are usually employed with a proportion of primary air of between 8% and 25% of the total quantity of combustion air.
The power of the burner, i.e. the operational working, is regulated by a respective reduction or increase of the fuel and the air admission within a determined range of adjustment, in which the minimum adjustable working for obtaining a stable flame is equal to about 20 to 25% of the maximum working possible.
When the burner is started, oil must, as a general rule, be injected through the central orifice of the nozzle and must be ignited in order to pre-heat the furnace, since combustion of the solid fuel, which is supplied concentrically, is possible only in a sufficiently pre-heated furnace.
With respect to this state of the art, the present invention has for its object to provide a process for exploiting a burner of a rotary tube furnace and also a burner adapted to carry out this process, which may operate with a smaller proportion of primary air and present a broader range of adjustment of the operational working.